1. Field of the Invention
This invention relates to systems used in analyzing real parameters of aircraft flight and producing visual flight profile data. In particular, the invention relates to a system for providing data indicating the most economical, the most fuel efficient, or long-range cruise profile depending upon real flight parameters.
2. Description of the Prior Art
Over the past few years, the cost of petroleum fuels and the cost of labor have greatly increased, affecting many industries, including the air transportation industry. Jet powered aircraft transport the majority of people who travel by air, particularly for overseas or other long distance flights. The amount of fuel consumed in one flight can be thousands of pounds. All commercial aircraft jets are capable of tremendous speeds. Some commercial jet aircrafts now exceed the speed of sound with faster speeds promised in the future.
The pilot's work has grown increasingly complex due to the high speeds, the large sizes of the jet aircraft, the increased air traffic, and the inherent complex nature of the forces acting to keep the jet aircraft in flight.
The pilot realizes that by flying the aircraft at certain speeds and certain altitudes he can get better performance from the aircraft. But in the time it would take to accurately figure out the correct speed and correct altitude, the pilot could be approaching the airport of destination. Therefore, in the past, booklets containing charts with various engine pressure ratios, altitudes and speeds have beem compiled for use by the pilot. The pilot looks through the charts and picks the closest profile that he wants to fly and still maintain adequate performance from his aircraft. However, slight discrepancies between the real parameters of the aircraft and the theoretical parameters used to obtain the charts can result in substantial error, resulting in excess fuel burned and excess time required in flight.
Several previous devices which have been used on aircraft use real variables of the aircraft and analyze the variables to produce signals which represent the optimum speed and altitude to obtain maximum distance to maximum endurance in the air. One such device is disclosed in U.S. Pat. No. 3,153,143 issued to Fogarty on Oct. 13, 1964. The Fogarty device utilizes real parameters, including weight and the change of weight as fuel is consumed, to compute the maximum range or maximum endurance.
Another such device is disclosed in U.S. Pat. No. 3,612,837 issued to Brandau on Oct. 12, 1971. The Brandau device has a warning indicator which is actuated when excessive fuel consumption is detected. The system uses real data of the flight to compute fuel reserves, time to target, and the range or endurance of the flight at different altitudes.
As opposed to military aircraft that are on a strategic flight where the time and endurance are main factors in determining whether the aircraft can hit a military target, the pilots of passenger aircraft are usually more concerned with how they can arrive at a destination with a minimum amount of fuel consumed and minimum cost per flight. Particularly with "jumbo jets" the crew of an aircraft can involve many people both on the ground and in the air. The wages of the crew are often directly dependent on the amount of time the flight takes. Time-dependent costs are lowered at greater speeds but it still may be undesirable to fly at the fastest possible speeds becaue fuel costs are increased due to increased consumption at greater speeds which may offset any gain in lower time-dependent costs.
While the air transportation company is concerned with total costs per flight, the pilots are mainly concerned with aircraft performance factors and cannot spend a great amount of time to calculate the proper speed to minimize total costs. The pilot has too many other factors to demand his attention. Not only must he know what his maximum speed or maximum altitude is, he also must take into consideration his engine pressure ratio limits for his jet engines. The engine pressure ratio limits are dependent on both the altitude and the speed at which his aircraft is flying. It also takes a great amount of time to calculate a safe maximum speed which is often desired without exceeding the certified engine pressure ratio limits of the jet engines.
Speed control devices have been utilized to control and maintain the speed of the aircraft. Some examples of speed control devices are disclosed in U.S. Pat. No. 3,998,411 to Blechen issued on Dec. 21, 1976, and U.S. Pat. No. 4,029,946 issued to Gerstine et al on June 14, 1977. The Gerstine reference discloses a converging control system which sends a progressively smaller signal to a throttle control as a moving object approaches the desired set speed so as to prevent overshooting. However, neither of the references disclose an on-board computer system in which the maximum safe speed is determined without exceeding the engine pressure ratio limit.
Not only must the pilot of the passenger jet craft determine the most efficient flight profile, he must also take into account the comfort of the passengers. It is known that fuel is used most efficiently when the engine pressure ratios are at a minimum. However, slight fluctuation in the engine pressure ratios results in a substantial difference in speed of the aircraft which can be uncomfortably felt by the passengers. When the fuel is used at only 99% efficiency rather than 100%, a substantially more comfortable flight with less speed fluctuations is obtained. Thus, for many long-range cruises, it is desirable that pilots set their aircraft into a flight profile which is commonly known as a long-range cruise profile. The calculations for the long-range cruise profile can be as difficult to obtain as the maximum speed profile or the minimum trip cost flight profile. Charts have been provided to pilots which provide certain profiles for certain flight parameters. As with the minimum fuel profiles, the charts do not necessarily reflect the real flight parameters of the aircraft or the degraded performance of the particular aircraft.
A performance data system is needed which receives signals indicating real flight parameters and produces, according to the desires of the pilot, a most economical flight profile, long-range cruise flight profile, the most fuel efficient flight profile, or the fastest speed or highest altitude possible within the engine pressure ratio limits of the jet engines.